Parameters Of Laser Radiation Research Articles

Processing and Functionalization of Vertical Graphene Nanowalls by Laser Irradiation.

The processing of vertical graphene nanowalls (VGNWs) via laser irradiation is proposed as a means to modulate their physicochemical properties. The effects of the number of applied pulses and fluence of each pulse are examined. Raman spectroscopy studies the effect of irradiation on the chemical structure of the VGNWs. Results show a decrease in density of defects and number of layers, which points toward a mechanism including evaporation of amorphous or loosely bonded C from defective points and recrystallization of graphene. Moreover, the effect of laser irradiation parameters on the morphology of Mo thin films deposited on VGNWs is investigated. The received thermal dosage results in the formation of particles. In this case, the number of pulses and pulse fluence are found to affect the size and distribution of these particles. The study provides a novel approach for the functionalization of VGNWs via laser irradiation, which can be extended to other graphene-based nanostructures.

Моделирование способов управления динамикой цианобактериального цветения с применением воздушных и надводных робототехнических средств

The paper discusses the problem of water areas contaminated with cyanobacteria and ways to eliminate it through the use of robotic means. Laser radiation has the ability to significantly suppress the vital activity of both cyanobacteria and a number of studied pathogenic bacteria, fungal viruses and other microorganisms. The parameters of laser radiation were modeled with an assessment of the inhibitory effect on cyanobacteria in water bodies. Examples of created attachments with laser emitters, transport unmanned aerial vehicles and surface vehicles used in studies to control the dynamics of cyanobacterial blooms are presented.

Metrological ensures for high-power laser radiation

The paper presents the state of ensuring the uniformity of measurements of energy parameters of high-power laser radiation. The research was carried out at the All-Russian Research Institute of Optical and Physical Measurements. The formation of a metrological support system for measuring the energy parameters of high-power continuous laser radiation required the creation of three standards, including one State primary standard of average laser power, and a line of four basic measuring instruments in the spectral range 1.07–10.6 μm and power range 1–500 kW. For the first time, a dynamic method for measuring high levels of laser power was developed and used. This ensured the certification of measuring instruments using reference radiation with a power of less than 100 kW. This has led to a significant increase in the level of metrological support for technological and special high-power laser equipment.

Selective neural inhibition via photobiomodulation alleviates behavioral hypersensitivity associated with small sensory fiber activation.

Photobiomodulation at higher irradiances has great potential as a pain-alleviating method that selectively inhibits small diameter nerve fibers and corresponding sensory experiences, such as nociception and heat sensation. The longevity and magnitude of these effects as a function of laser irradiation parameters at the nerve was explored. In a rodent chronic pain model (spared nerve injury-SNI), light was applied directly at the sural nerve with four delivery schemes: two irradiance levels (7.64 and 2.55 W/cm2 ) for two durations each, corresponding to either 4.8 or 14.4 J total energy, and the effect on sensory hypersensitivities was evaluated. At emitter irradiances of 7.64 W/cm2 (for 240 s), 2.55 W/cm2 (for 720 s), and 7.64 W/cm2 (for 80 s) the heat hypersensitivity was relieved the day following photobiomodulation (PBM) treatment by 37 ± 8.1% (statistically significant, p < 0.001), 26% ± 6% (p = 0.072), and 28 ± 6.1% (statistically significant, p = 0.032), respectively, and all three treatments reduced the hypersensitivity over the course of the experiment (13 days) at a statistically significant level (mixed-design analysis of variance, p < 0.05). The increases in tissue temperature (5.3 ± 1.0 and 1.3 ± 0.4°C from 33.3°C for the higher and lower power densities, respectively) at the neural target were well below those typically associated with permanent action potential disruption. The data from this study support the use of direct PBM on nerves of interest to reduce sensitivities associated with small-diameter fiber activity.

MODELING OF TEMPERATURE GRADIENTS DURING THE INTERACTION OF LASER RADIATION WITH BIOLOGICAL TISSUE

Modeling thermal gradients in biological tissues, when interacting with laser radiation, helps to understand how heat flows are distributed in the body and reflect heating zones. The main aspects of the simulation include the parameters of the laser source, such as the wavelength and power, the initial temperature conditions of the tissues, as well as the use of special numerical methods that help to optimally solve the heat conduction equations and visualize the obtained results. Temperature distribution in tissues plays an important role in determining the effectiveness and safety of laser treatment. This allows you to choose effective parameters of laser radiation and irradiation modes to achieve the desired result without negative consequences for the patient. However, it is important to consider that the actual behavior of tissues in response to laser radiation may be more complex due to the physiological characteristics of each person.Therefore, all models and calculations must take into account this feature and diversity and take into account safety regulations. Laser treatment should be carried out under the supervision of qualified specialists, in particular doctors who have relevant knowledge and experience in the field of medicine. This approach helps ensure the safety and effectiveness of laser procedures for patients. Modeling the distribution of tissue thermal gradients when interacting with laser radiation plays an important role in the development of modern medicine and scientific research and provides efficiency compared to the obtained experimental data. It helps to improve the understanding of thermal processes in biological tissues and to ensure the safety of patients receiving laser treatment. In this work, experiments were conducted on the effect of laser irradiation on biological tissue, as well as modeling of changes in temperature gradients during the effect of laser irradiation on biological tissue, using various models of heat and mass transfer, using the Matlab software environment. As a result of the modeling in this work, the patterns of changes in temperature gradients were obtained, which were compared with the experimentally obtained data, the errors of Pennes models and finite element methods, finite differences were analyzed, and conclusions were drawn.

Multiwavelength Fluorescence and Diffuse Reflectance Spectroscopy for an In Situ Analysis of Kidney Stones

This study explores the use of diffuse reflectance spectroscopy (DRS) and multiwavelength fluorescence spectroscopy for real-time kidney stone identification during laser lithotripsy. Traditional methods are not suitable for in situ analysis, so the research focuses on optical techniques that can be integrated with lithotripsy fibers. Experiments were conducted ex vivo, using DRS and multiwavelength fluorescence spectroscopy (emission–excitation matrix (EEM)) to distinguish between 48 urinary stones of three types: urate, oxalate and hydroxyapatite, with infrared spectroscopy as a reference. A classification model was developed based on EEM and DRS data. Initial classification relying solely on EEM data achieved an f1-score of 87%, which increased to 92% when DRS data were included. The findings suggest that optical spectroscopy can effectively determine stone composition during laser lithotripsy, potentially enhancing surgical outcomes via the real-time automatic optimization of laser radiation parameters.

Surface-Enhanced Raman Scattering Studies of Au-Ag Bimetallic Nanoparticles with a Tunable Surface Plasmon Resonance Wavelength Synthesized by Picosecond Laser Irradiation

Here, we present a simple and green method of preparing Au-Ag bimetallic nanoparticles (NPs) with a tunable surface plasmon resonance (SPR) wavelength by using picosecond laser irradiation. Au-Ag alloy NPs have been produced by irradiating the solutions containing respective metallic salts in a polyvinyl alcohol (PVA) matrix using a picosecond laser in a single-step process. The SPR wavelength of the Au-Ag bimetallic NPs is observed to be shifted/changed with the Au-Ag concentration and the laser irradiation parameters. The Au-Ag NPs embedded in the PVA matrix are advantageous for Surface-Enhanced Raman scattering (SERS) applications. The estimated enhancement factors (EFs) were observed to vary as a function of conditions of the Au-Ag bimetallic alloy NPs synthesis and also on the concentration of Au at a fixed input fluence of irradiation. The SERS active platforms of Au-Ag bimetallic NPs showed EFs as high as of the order of 108 for Crystal Violet (CV) dye samples at nano molar concentrations. The present study demonstrates a simple, single-step, and green method that fabricates Au-Ag alloy-based nanocomposites suitable for SERS investigations with significantly higher orders of EFs.

Laser-Assisted Structuring of Graphene Films with Biocompatible Liquid Crystal Polymer for Skin/Brain-Interfaced Electrodes.

The work presented here introduces a facile strategy for the development of flexible and stretchable electrodes that harness the robust characteristics of carbon nanomaterials through laser processing techniques on a liquid crystal polymer (LCP) film. By utilizing LCP film as a biocompatible electronic substrate, control is demonstrated over the laser irradiation parameters to achieve efficient pattern generation and transfer printing processes, thereby yielding highly conductive laser-induced graphene (LIG) bioelectrodes. To enhance the resolution of the patterned LIG film, shadow masks are employed during laser scanning on the LCP film surface. This approach is compatible with surface-mounted device integration, enabling the circuit writing of LIG/LCP materials in a flexible format. Moreover, kirigami-inspired on-skin bioelectrodes are introduced that exhibit reasonable stretchability, enabling independent connections to healthcare hardware platforms for electrocardiogram (ECG) and electromyography (EMG) measurements. Additionally, a brain-interfaced LIG microelectrode array is proposed that combines mechanically compliant architectures with LCP encapsulation for stimulation and recording purposes, leveraging their advantageous structural features and superior electrochemical properties. This developed approach offers a cost-effective and scalable route for producing patterned arrays of laser-converted graphene as bioelectrodes. These bioelectrodes serve as ideal circuit-enabled flexible substrates with long-term reliability in the ionic environment of the human body.

Scaling laws for the additive manufacturing of the AISI 316 L deposited by laser surface cladding and direct metal deposition methods

This study presents a comparative analysis of the shape and microstructure of individual tracks formed from AISI 316 L stainless steel using laser surface cladding (LSC) and direct metal deposition (DMD) methods. The research aims to identify the relationship between laser radiation parameters (laser spot size, radiation power, scanning speed) and geometric characteristics of created tracks. The result shows that the change in the geometric characteristics of single tracks (depth, width, and height) can be related to two dimensionless parameters: normalized enthalpy H and Peclet number Pe. Based on the experimental data summary, the limiting values of the conditions for realizing keyhole melting (H > 2, Pe < 10) and heat conduction (H < 2, Pe > 10) were determined.

Unraveling the parameters and biological mechanisms of CO2 laser therapy for acute pain relief.

Acute pain-related pathology is a significant challenge in clinical practice, and the limitations of traditional pain-relief drugs have made it necessary to explore alternative approaches. Photobiomodulation (PBM) therapy using CO2 laser has emerged as a promising option. In this study, we aimed to identify the optimal parameters of CO2 laser irradiation for acute pain relief through in vivo and in vitro experiments. First, we validated the laser intensity used in this study through bone marrow mesenchymal stem cells (BMSCs) experiments to ensure it will not adversely affect stem cell viability and morphology. Then we conducted a detailed evaluation of the duty cycle and frequency of CO2 laser by the hot plate and formalin test. Results showed a duty cycle of 3% and a frequency of 25 kHz produced the best outcomes. Additionally, we investigated the potential mechanisms underlying the effects of CO2 laser by immunohistochemical staining, and found evidence to suggest that the opioid receptor may be involved in its analgesic effect. In conclusion, this study provides insights into the optimal parameters and underlying mechanisms of CO2 laser therapy for effective pain relief, thereby paving the way for future clinical applications.

Surface structured silver-copper bimetallic nanoparticles by irradiation of excimer laser pulses to bilayer thin films

Optical chips based on plasmonic bimetal nanoparticles are of particular interest for various applications, including optical sensors, as well as plasmon-enhanced fluorescence and plasmon-enhanced Raman scattering due to their extraordinary optical properties. In the paper, the formation of the bimetallic nanoparticles on the BK7 substrate and tuning of the LSPR wavelengths by irradiation of excimer laser pulses (193 nm output wavelength and 15 ns temporal pulse linewidth) to silver-copper thin films deposited by the physical vapor deposition (PVD) method is studied. Applying four and five ArF laser pulses with the fluence of 140 mJ cm−2 leads to the formation of spherical Ag-Cu nanoparticles and clusters, respectively, with several LSPR peaks in the UV and visible ranges. Also, sharp and intense LSPR peaks in the 560 to 700 nm spectral range are observed in the absorption spectra of the produced samples with four laser pulses which indicates the ability of the method for tuning the LSPR wavelength. Furthermore, the highest enhancement in the Raman scattering of R6G solution is provided using this sample as a substrate for Raman spectroscopy. Therefore, the laser-produced spherical Ag-Cu NPs by these parameters of laser irradiation can be a good candidate for applications based on LSPR, and Raman or fluorescence enhancement.

Molecular Dynamics Modeling of Pulsed Laser Fragmentation of Solid and Porous Si Nanoparticles in Liquid Media.

The production of non-toxic and homogeneous colloidal solutions of nanoparticles (NPs) for biomedical applications is of extreme importance nowadays. Among the various methods for generation of NPs, pulsed laser ablation in liquids (PLAL) has proven itself as a powerful and efficient tool in biomedical fields, allowing chemically pure silicon nanoparticles to be obtained. For example, laser-synthesized silicon nanoparticles (Si NPs) are widely used as contrast agents for bio visualization, as effective sensitizers of radiofrequency hyperthermia for cancer theranostics, in photodynamic therapy, as carriers of therapeutic radionuclides in nuclear nanomedicine, etc. Due to a number of complex and interrelated processes involved in the laser ablation phenomenon, however, the final characteristics of the resulting particles are difficult to control, and the obtained colloidal solutions frequently have broad and multimodal size distribution. Therefore, the subsequent fragmentation of the obtained NPs in the colloidal solutions due to pulsed laser irradiation can be utilized. The resulting NPs' characteristics, however, depend on the parameters of laser irradiation as well as on the irradiated material and surrounding media properties. Thus, reliable knowledge of the mechanism of NP fragmentation is necessary for generation of a colloidal solution with NPs of predesigned properties. To investigate the mechanism of a laser-assisted NP fragmentation process, in this work, we perform a large-scale molecular dynamics (MD) modeling of FS laser interaction with colloidal solution of Si NPs. The obtained NPs are then characterized by their shape and morphological properties. The corresponding conclusion about the relative input of the properties of different laser-induced processes and materials to the mechanism of NP generation is drawn.

Laser induced graphene (LIG) biosensors derived from chitosan: Towards sustainable and green electronics

Modern biosensors can provide real-time monitoring of individuals' health status, revolutionizing traditional healthcare diagnostics. As demand for these devices is continuously growing, the development of novel green materials and processes is mandatory to ensure sustainability. In this work, a simple laser direct writing approach was utilized to fabricate a novel green Laser Induced Graphene (LIG) glucose biosensor, whereby chitosan-based biofilms were used as writing feedstock material. Careful optimization of the biofilm composition was carried out in conjunction with the optimization of laser irradiation parameters to obtain bio-LIG structures with low sheet resistance and spectral characteristics of graphene-like materials. The surface of bio-LIG electrodes was modified with Prussian Blue nanoparticles and the electrocatalytic performance of bio-LIG sensors towards H2O2 was investigated using voltammetric techniques. The response of H2O2 was linear in the range 3 μM - 1 mM (sensitivity, 103.4 μA mM−1 cm−2 and the limit of detection (LOD), 1.9 μM). Following immobilization of glucose oxidase, the bio-LIG sensors showed a linear response of glucose in phosphate buffer (PBS) in the relevant physiological range of 25–300 μM (sensitivity, 457 nA mM−1 cm−2). The LOD was calculated as 9.6 μM. Additionally, the biosensor showed comparable results in artificial sweat.

A More Controllable Laser Reduction of Graphene Oxide Membrane for Electrode Applications

Reduced graphene oxide (rGO) has attracted significant attention as an active electrode material for sensors and flexible energy devices due to its high electric conductivity and large surface area. rGO is usually obtained from graphene oxide(GO) through a thermal, chemical, photochemical, and electrochemical reduction process. Compared to the other reduction strategy, laser reduction is a single-step, precise, low cost, and chemical-free processing that can be directly applied on the GO membrane at room temperature in an ambient condition.The laser irradiation parameter, such as laser source, power, speed, and frequency, plays an important role in reduction optimization. In general, the quality of the rGO is not as high as that of pristine graphene because of incomplete reduction, and oxygenated defects involved in the reduction process.The not fully removed oxygenated function group not only influence the sensitivity and selectivity of the electrode, but also influences response time and recovery time during sensing and the electrochemical window of the supercapacitor made with those rGO electrode.This study aims to develop reduced graphene oxide (rGO) through laser irradiation for application in supercapacitors and electrochemical sensors as electrodes. GO membranes were fabricated with a layer-by-layer assembly process first then further reduced through conventional CO2 laser reduction. The laser irradiation parameters including intensity, frequency, and scan speed will be optimized to achieve the reduction up to maximi, C/O ratio. The effects of the reduction will be characterized and evaluated using scanning electron microscope (SEM), Fourier Transform Infrared (FTIR) spectroscopy, Raman spectroscopy, X-ray diffraction (XRD)spectroscopy, and four-point probe station. The influence of the humidity on the impedance of the rGO electrode and the capacitance of the planar supercapacitor made with rGO electrode will also be analyzed for potential application of as-prepared rGO electrodes in supercapacitors and humidity sensors.

Graphene Oxide Membranes: Controlled Laser Reduction for Sensing Applications

Reduced graphene oxide (rGO) has attracted attention as an active electrode material for flexible electrochemical devices due to its high electric conductivity and large surface area. Compared to other reduction processes, laser reduction is a precise, low-cost, and chemical-free process that is directly applied to graphene oxide (GO) membranes. This study aims to develop rGO through laser irradiation for application as electrodes in thin flexible electrochemical sensors. Laser irradiation parameters will be optimized to achieve reduction of a low oxygen to carbon (O/C) ratio and surface impedance. The influence of humidity on the impedance of rGO electrodes will be studied. The observed instability of the rGO electrode is related to incomplete reduction and oxygenated defects involved in reduction. Partially removed oxygenated functional groups not only influence the impedance of the electrode but make it sensitive to the humidity of the working environment. The result provides references for GO’s laser reduction optimization, demonstrates the potential of applying rGO as an electrode in sensing applications, but also reveals the limitation of applying the laser reduced rGO electrode in a non-constant humidity environment.

Study of the Effect of Laser Radiation Parameters on the Efficiency of Lithotripsy

In this article, we report on experimental studies of the influence of several laser radiation parameters, such as the duration of the laser pulse, the radiation wavelength, and the pulse energy, on the efficiency of the destruction of urinary calculi. The study used a laser lithotripter based on a fiber Tm laser generating at a wavelength of 1940 nm with pulses with a duration of about 1800 μs and pulse energy of up to 6 J, as well as a femtosecond solid-state Yb laser generating at a wavelength of 1032 nm with a pulse duration of about 250 fs and pulse energy of up to 400 μJ. A comparative analysis was carried out according to such criteria as the productivity of lasers when removing a unit mass of images and the amount of sample displacement resulting from the retropulsion effect. The results obtained in this work demonstrated that the femtosecond laser loses approximately two times its efficiency in terms of sample material removal. However, this shows the absolute advantage of the photoionization mechanism of femtosecond laser ablation in the study of retropulsion and thermal heating, which were completely absent in this case.

Laser‐Assisted Direct Ink Writing for High‐Fidelity Fabrication of Elastomeric Complex Structures

AbstractPolydimethylsiloxane (PDMS) is extensively applied in the 3D printing field due to its excellent biocompatibility, flexibility, and gas permeability. However, as a thermal curing material, its low strength before curing inevitably causes structural deformation during the printing process and deteriorates the shape accuracy. In this paper, an innovative method, the infrared laser‐assisted direct ink writing (DIW) process, is developed to realize the in situ preheating and curing of silicone materials to improve the strength of PDMS filaments during processing. Therefore, the large‐span spatial structure with high‐fidelity morphology can be produced. First, the feasibility is validated that temperature ascension of the voxels arising from the irradiation energy of the infrared laser can accelerate the cross‐linking reaction and realize the precuring of PDMS; then, the relationship between the parameters of laser irradiation and the processing performance of 3D printing is systematically investigated to find the optimization. Finally, experiments are conducted, including the single silicone filament, silicone foams, and complex 3D features. Their excellent structural preservation proves the proposed method is practical to fabricate the high‐fidelity fabrication of complex structures such as large spans and thin wall features, which will help to broaden the 3D printing capabilities of silicone in the development of flexible electronics and soft robots.

Effect of an low-energy Nd: YAG laser on periodontal ligament stem cell homing through the SDF-1/CXCR4 signaling pathway

BackgroundThe key to the success of endogenous regeneration is to improve the homing rate of stem cells, and low-energy laser is an effective auxiliary means to promote cell migration and proliferation. The purpose of this study was to observe whether low-energy neodymium (Nd: YAG) laser with appropriate parameters can affect the proliferation and migration of periodontal ligament stem cells (PDLSCs) through SDF-1/CXCR4 pathway.Methodsh PDLSCs were cultured and identified. CCK8 assay was used to detect the proliferation of h PDLSCs after different power (0, 0.25, 0.5, 1, and 1.5 W) Nd: YAG laser (MSP, 10 Hz, 30 s, 300 μ m) irradiation at 2th, 3rd,5th, and 7th days, and the optimal laser irradiation parameters were selected for subsequent experiments. Then, the cells were categorized into five groups: control group (C), SDF-1 group (S), AMD3100 group (A), Nd: YAG laser irradiation group (N), and Nd: YAG laser irradiation + AMD3100 group (N + A). the migration of h PDLSCs was observed using Transwell, and the SDF-1 expression was evaluated using ELISA andRT-PCR. The SPSS Statistics 21.0 software was used for statistical analysis.ResultsThe fibroblasts cultured were identified as h PDLSCs. Compared with the C, when the power was 1 W, the proliferation rate of h PDLSCs was accelerated (P < 0.05). When the power was 1.5 W, the proliferation rate decreased (P < 0.05). When the power was 0.25 and 0.5 W, no statistically significant difference in the proliferation rate was observed (P > 0.05). The number of cell perforations values as follows: C (956.5 ± 51.74), A (981.5 ± 21.15), S (1253 ± 87.21), N (1336 ± 48.54), and N + A (1044 ± 22.13), that increased significantly in group N (P < 0.05), but decreased in group N + A (P < 0.05). The level of SDF-1 and the expression level of SDF-1 mRNA in groups N and N + A was higher than that in group C (P < 0.05) but lower than that in group A (P < 0.05).ConclusionsNd: YAG laser irradiation with appropriate parameters provides a new method for endogenous regeneration of periodontal tissue. SDF-1/CXCR4 signaling pathway may be the mechanism of LLLT promoting periodontal regeneration.

Effect of physical parameters of laser radiation on the process of weld formation in transparent dielectrics

The article determines the influence of pulse duration, energy density and focusing parameters on the process of formation of a weld of transparent dielectrics. A comparative analysis of laser welding of borosilicate and quartz glass with different pulse durations and energies of picosecond and femtosecond fiber lasers was carried out. Basic regularities of weld shape change depending on pulse duration and energy are obtained. The combination of physical parameters of laser radiation and focusing allows welding along gaps up to 6 μm.

Problems and prospects in the treatment of various forms of pigmented nevi in children (a literature review)

Introduction. Pigmented nevi (PN) are formations in the skin layers which consist of accumulated melanocytes of various differentiation degrees and located in different layers of the skin. In modern society, this pathology causes serious medical and psychological problems; not infrequently , one can see unsatisfactory clinical and aesthetic outcomes. There is no any clear tactics which could take into account PN forms, location and child’s age. Purpose. To study modern problems and to outline prospects for treating various PN forms in children using the information obtained after literature search for the period 2005–2022. Material and methods. The authors made the literature search in domestic and foreign databases for the period 2005–2022. The following key words were used for the search: benign melanocytic skin lesions; pigmented nevus; laser radiation. 1627 literature sources were studied, 87 works were included in the review. Results. Despite of various techniques used for PN removal, unsatisfactory results are still noted in 41 % of patients with a complication rate of up to 50 %. After implementation laser scalpel for PN removal, complications in the form of hypertrophic and keloid scars were noted in 2–5 % of patients, postoperative hyperemia- in 21 % of cases, hyperpigmentation in 13 % and hypopigmentation in 34 %. The present review outlines advantages and disadvantages of various modalities used for removing PN. The authors also underline that the most promising ones are laser techniques in which laser light has a specific selectivity to pigmented tissues. The article has no information on parameters of laser irradiation which are required for treating definite forms of PN in children. Conclusion. Further research is needed to optimize existing and to develop new laser light techniques for treating various PN forms which should bring a significant improvement in outcomes.